The Frequency of Errors in Determining Age Based on Selected Features of the Incisors of Icelandic Horses.
Authors: Łuszczyński Jarosław, Pieszka Magdalena, Petrych Weronika, Stefaniuk-Szmukier Monika
Journal: Animals : an open access journal from MDPI
Summary
Dental age estimation in horses relies on consistent ontogenetic patterns, yet this method produces substantial errors—particularly across different breeds. Łuszczyński and colleagues examined 126 Icelandic horses (ages 0–24 years) with an experienced assessor blinded to actual age, comparing estimated ages against verified breeding records to quantify misclassification rates across four age cohorts. Overall accuracy proved disappointing: 36.5% of horses were incorrectly aged, with systematic underestimation averaging 0.9 years and overestimation averaging 1.3 years; critically, horses aged over two years showed error rates of 40–68% depending on which incisor feature was evaluated, whilst the youngest group (0–2 years) achieved only 2.1% error. The poor performance of traditional eruption and cup-disappearance criteria in older Icelandic horses suggests this breed exhibits a materially slower dental maturation timeline than continental warmbloods, implying that breed-specific growth curves should inform age assessment rather than applying universal standards. For practitioners, these findings underscore the need for caution when estimating age in Icelandic and potentially other native breeds, and highlight an urgent requirement for breed-tailored reference data to improve the reliability of dental age determination in clinical and forensic contexts.
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Practical Takeaways
- •Standard age determination methods using incisor features are unreliable in Icelandic horses, with over one-third of age estimates being incorrect—use breeding documentation when available rather than relying on dental assessment alone
- •Young Icelandic horses (0-2 years) can be aged relatively accurately from deciduous incisor eruption and cup wear, but horses >2 years become difficult to age due to breed-specific slower tooth development
- •Age underestimation is common when assessing permanent incisor eruption in Icelandic horses, while cup disappearance tends to lead to overestimation—practitioners should apply breed-specific corrections or seek alternative confirmation methods
Key Findings
- •Age estimation based on incisor examination had a 36.5% error rate in Icelandic horses
- •Young horses aged 0-2 years had significantly lower error rates (2.1%) compared to older horses (40-68% errors depending on feature assessed)
- •Age was underestimated in 19.0% of cases (average 0.9 ± 1.0 years) and overestimated in 17.5% (average 1.3 ± 1.4 years)
- •Icelandic horses up to 5 years show slower growth and tooth development rates compared to warmblood breeds, suggesting breed-specific patterns are needed for accurate age determination